The Saemangeum Basin has been subjected to water quality issues following the construction of a seawall downstream of the Mangyeong River and Dongjin River. Various structural measures have been discussed, but none have been effective so far. In this study, the change in management water level was proposed as a countermeasure, and Delft3D was used to investigate the change in water quality according to the management water levels. Future operations, including the interruption of seawater inflow, were considered. Based on three assumptions for simulating the operation of the drainage gate, the condition of Saemangeum in 2030 when the Master plan is completed was modeled. COD and T-N were selected as the pollutant indicators. The boundary conditions and numerical analysis input data were obtained by integrating actual field data and operation logs. The numerical analysis showed that the water level was more advantageous for water quality when the water level was increased by 0.10m from the current management level of EL.(-)1.5m. It was also confirmed that contaminant diffusion in Mangyung and Dongjin was not actively progressing through the new connecting canal.

Background/Objectives: Due to the extreme climate and the localized heavy rain, the frequency of debris flow has been increasing. Therefore, there is a growing expectation for accurate numerical analysis.Methods/Statistical analysis: We present a prediction method that can calculate the propagation length of the debris flow. This analysis indicates the relationship between the potential energy and the propagation length of the debris flow. To study the behavior of the debris flow accurately, the change in the momentum force must be considered; otherwise the calculation accuracy of the debris flow behavior is inevitably low.Findings: Entrainment is a common behavior in a debris flow that leads to changes in the momentum force. Here, we analyzed the change in the momentum force using a 2D simulation model that included entrainment. The results show how the debris flow behaves with changes in the momentum force. When entrainment is considered, the propagation length tends to be underestimated. With detailed information, the uncertainty in the prediction accuracy can be reduced.Improvements/Applications: If studies on the material properties of debris flow would be added, it will be possible to carry out various and accurate analysis of the debris flow

No abstract

No abstract

Imha Reservoir has both a water transfer tunnel connecting Andong Reservoir and a selective withdrawal facility (SWF), which enable the innovative operation of the reservoir. Although these facilities had not been equipped when constructed in 1993, these structural measures were applied afterward as needed for the effective reservoir operation. The tunnel was constructed in 2015 to minimize the spillway discharge of a reservoir during floods by moving water to the other reservoir with free space. The SWF was installed in 2006 to address problems due to the persistent turbidity of Imha Reservoir. The effectiveness of these facilities was demonstrated through the operational cases in October 2019, while some improvements to non-structural measures were derived simultaneously. To prevent damage to the fish ecosystem of Imha reservoir, the tunnel currently was operated in a one-way water movement. However, a two-way water movement should be allowed as designed in the mid to long term. The SWF was operated effectively based on the prediction of the fate and transport of turbid water inside the reservoir using CE-QUAL-W2. Nevertheless, more action procedures on turbid water are required, such as setting clear criteria for the release timing of turbid water, predicting the downstream turbidity variations, etc.